Method and apparatus for performing double-sided refill friction stir spot welding

Abstract

To provide a method for performing simultaneous double-sided refill friction stir spot welding.SOLUTION: A method includes: providing a first welding head (110) having a first probe member (102) and a first tubular shoulder (104); providing a second welding head (210) having a second probe member (202) and a second tubular shoulder (204); arranging the first welding head (110) on a first surface, so that the first probe member (102) and the first tubular shoulder (104) are brought into contact with a first surface of a welding object; and arranging the second welding head (210) on a second surface of a welding object (112), which faces the first surface.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a method for performing refill friction stir spot welding.

Background Art

[0002] Joining two components together by welding is a well-known process. Typically, the welding method involves bringing two metals into contact and fixing them, applying heat to a consumable material (e.g., in the form of a consumable electrode), melting the consumable material as well as a part of the material to be welded, and then cooling this to form a weld joint.

[0003] This conventional welding technique is an effective way to create a strong joint between two materials, but it also has drawbacks. For example, it requires the use of a consumable material, which means that there must be an equally continuous supply of the consumable material for continuous welding. Furthermore, the introduction of a second material into the welding process can create opportunities for impurities and weaknesses in the components of the weld joint, for example, when the consumable material has not been manufactured to a sufficiently high quality.

[0004] A method to overcome the need for a consumable material is provided by the invention of friction stir welding by the Welding Institute in the United Kingdom. Friction stir welding is a solid-state joining process that uses the frictional heat generated by a rotating tool to join materials and does not require the use of a consumable material.

[0005] Friction stir spot welding (FSSW) is a solid-state joining technique derived from friction stir welding (FSW). Unlike FSW, FSSW does not involve the linear movement of the tool and results in a specific "spot" weld joint. This technique has attracted interest in many industries, but its industrial adoption is limited mainly because end holes are generated.

[0006] In response to these concerns, a further technique known as Refill Friction Stir Spot Welding (FSSW) was developed. Outlined in International Publication No. 01 / 36144, this innovative technique utilizes a redesigned tool to achieve a spot weld without a terminal hole by rotating both the probe and the shoulder while simultaneously retracting the tubular shoulder surrounding the probe, while advancing the probe into the workpiece. During this movement, the material, plasticized by friction between the probe and the workpiece and pressed by the advancing probe, is received in the space between the probe and the tubular shoulder. When the probe has advanced to a certain depth into the workpiece, the combined movement is reversed, resulting in the probe retracting while the shoulder advances toward the workpiece, pushing the displaced material back into the recess created by the probe.

[0007] This conventional method of refill FSSW avoids the use of consumables and end holes, but it still has certain limitations. For example, the weld depth is limited by the plunge depth of the refill FSSW machine. As a result of this limitation, it may not be possible to weld thick joints, or the welding time will be long, and the previous weld will deteriorate when welding is performed one after the other.

[0008] Furthermore, challenges in welding multi-stack joints such as Al-Ti-Al or Al-St-Al arise due to the high melting temperatures of the intermediate materials. Because of this elevated melting point, fusion welding or conventional refill FSSW becomes impractical in such applications. [Overview of the project] [Problems that the invention aims to solve]

[0009] The object of the present invention is to overcome the aforementioned drawbacks while providing further advantages, as described herein. [Means for solving the problem]

[0010] One aspect of the present invention relates to a method for performing refill friction stir spot welding. The method includes the steps of providing a first welding head comprising a first probe member and a first tubular shoulder, wherein the first probe member is positioned inside the first tubular shoulder and is axially aligned with the first tubular shoulder along the first head axis; and providing a second welding head comprising a second probe member and a second tubular shoulder, wherein the second probe member is positioned inside the second tubular shoulder and is axially aligned with the second tubular shoulder along the second head axis. The method includes the steps of: positioning a first welding head on a first surface such that a first probe member and a first tubular shoulder contact a first surface of the workpiece to be welded; and positioning a second welding head on a second surface opposite the first surface such that a second probe member and a second tubular shoulder contact a second surface of the workpiece to be welded and the first head axis is aligned with the second head axis. The method includes the steps of: simultaneously rotating the first and second welding heads so as to form an increased plastic volume in the workpiece in close proximity to (and in contact with) the first and second welding heads; simultaneously advancing one of the first probe member and the first tubular shoulder, and the other of the second probe member and the second tubular shoulder, from their initial positions along their respective first and second head axes to their respective first and second surfaces on the workpiece, while retracting the other of the first probe member and the first tubular shoulder, and the other of the second probe member and the second tubular shoulder, from their initial positions (for example, in the opposite direction) along their respective first and second head axes. The method also includes the steps of returning each of the first and second probe members and the first and second tubular shoulders toward their initial positions; and removing the first and second welding heads from their respective first and second surfaces on the workpiece.

[0011] When used, this method may be used to bring a weld to a workpiece by positioning a first welding head on the first surface of the workpiece and a second welding head on the second surface of the workpiece, and simultaneously advancing both the first and second welding heads into the workpiece to plasticize the volume of the workpiece, thereby generating a weld volume of the workpiece extending from both the first and second surfaces of the workpiece. When the described method is applied to both the first and second surfaces of the workpiece, heat loss that would normally occur through the back surface of the workpiece (e.g., the second surface) can be avoided. In fact, heat penetrating the workpiece from the first surface to the second surface can increase the efficiency of bringing a weld to the second surface, and vice versa. Furthermore, as the supplied heat increases, it becomes possible to plasticize materials that require more energy, enabling the realization of deeper welds. Thus, a synergistic effect is achieved compared to performing welding on a single surface. Furthermore, the weld volume may be large and may extend across the entire thickness of the workpiece, thereby increasing the strength of the weld compared to welding only one surface of the workpiece in a given time. In particular, welding from both sides simultaneously makes it possible to weld a joint twice as thick as that achievable with conventional refill FSSW processes in a single step.

[0012] The method may include the step of simultaneously advancing the first and second tubular shoulders from their initial positions along their respective first and second head axes into their respective first and second surfaces on the workpiece, while retracting the first and second probe members from their initial positions along their respective first and second head axes. The initial positions may correspond to the positions of the first and second probe members and tubular shoulders in contact with the workpiece before the rotation of the first and second probe members and the first and second tubular shoulders. Thus, the method may include the step of positioning the first and second probe members and the first and second tubular shoulders in contact with their respective first and second surfaces on the workpiece, wherein the first and second probe members and the first and second tubular shoulders are stationary with respect to rotation (e.g., not rotating relative to each other or to the workpiece).

[0013] The workpiece to be welded may comprise first and second components positioned between first and second welding heads, the first component comprising a first surface, and the second component comprising a second surface, and the method comprising the steps of advancing a first tubular shoulder into the workpiece by a distance less than or equal to the thickness of the first component, and advancing a second tubular shoulder into the workpiece by a distance less than or equal to the thickness of the second component. The first and second components may be in the form of sheets of the material to be welded, such as a sheet of aluminum. The workpiece to be welded may also be in the form of a welding stack, in which case the resulting weld may be in the form of a multi-stack joint. In particular, the method of the present invention is suitable for spot welding of aluminum and aluminum alloys, magnesium and magnesium alloys, and copper and copper alloys, and combinations thereof. Furthermore, spot welding of thermoplastic polymers and polymer matrix composites and combinations thereof may also be produced by the method of the present invention. Furthermore, titanium and titanium alloys, as well as steel components, can also form part of the workpiece subjected to the method of the present invention, but it should be noted that in the case of these materials, it is preferable that the probe member and / or tubular shoulder do not penetrate the components of these materials. Finally, the present invention is not limited to the examples of materials described above.

[0014] The method may include the step of simultaneously advancing the first tubular shoulder and the second probe member from their initial positions along their respective first and second head axes into the respective first and second surfaces of the workpiece to be welded, while simultaneously retracting the first probe member and the second tubular shoulder from their initial positions along their respective first and second head axes. By advancing the probe member of one welding head and the tubular shoulder of the other welding head, the user can obtain a desirable shape and / or structure of the weld.

[0015] The workpiece to be welded comprises first and second components positioned between first and second welding heads, wherein the first component has a first surface and the second component has a second surface. The method may include the steps of advancing a first tubular shoulder into the workpiece by a distance greater than the thickness of the first component, and advancing a second probe member into the workpiece by a distance greater than the thickness of the second component. By advancing the first tubular shoulder into the workpiece by a distance greater than the thickness of the first component, a weld with particularly high mechanical mixing of the first and second components can be created, which can improve the integration of the weld volume into the welded first and second components.

[0016] More preferably, the distance the first shoulder advances into the workpiece may be only slightly greater than the thickness of the first component, so that only the surface area of ​​the second component adjacent to the first component is essentially affected, i.e., the first shoulder merely "grabs" the second component. Similarly, in this more preferred embodiment, the distance the second probe member advances into the workpiece may be only slightly greater than the thickness of the second component, so that only the surface area of ​​the first component is essentially affected by the second probe member, i.e., the second probe member merely "grabs" the first component. This embodiment has been proven to result in a particularly stable joint.

[0017] The method may include the step of advancing the first tubular shoulder and the second probe member into the workpiece so that the second probe member is partially positioned within the first tubular shoulder. This helps to facilitate mixing of the first and second components when the probe member and tubular shoulder are returned to their original positions.

[0018] The workpiece to be welded may include a third component positioned between the first and second components, and the method includes the steps of advancing one of the first probe member and the first tubular shoulder into the workpiece along the first head axis by a distance greater than, equal to, or less than the thickness of the first component, and advancing one of the second probe member and the second tubular shoulder into the workpiece along the second head axis (208) by a distance greater than, equal to, or less than the thickness of the second component, while retracting the other of the first probe member and the first shoulder, and the other of the second probe member and the second shoulder, from their initial positions along their respective first and second axes. The third component may have lower plasticity than the first and second components at a given temperature. The third component may have a higher melting point than the first and second components. The first and second components may be made from the same first material, while the third component may be made from the second material. For example, the first and second components may be made from aluminum, while the third component may be made from titanium. Thus, the third component may be welded to the first and second components, thereby providing a high-strength multi-stack joint. More preferably, the distance the first probe member or first shoulder advances into the workpiece may be only slightly greater than the thickness of the first component, so that only the surface area of ​​the third component adjacent to the first component is essentially affected, i.e., the first probe member or shoulder merely "grabs" the third component. Similarly, in this more preferred embodiment, the distance the second probe member or second shoulder advances into the workpiece may be only slightly greater than the thickness of the second component, so that only the surface area of ​​the third component is essentially affected by the second probe member or second shoulder, i.e., the second probe member or second shoulder merely rubs against the third component.

[0019] The method may also include the step of advancing the first and second probe members from their initial positions along their respective first and second head axes into their respective first and second surfaces of the workpiece, while retracting the first and second tubular shoulders from their initial positions along their respective first and second head axes. By advancing the probe members of the welding head in parallel, the user can provide a specific shape and / or structure of the weld. In particular, the intermixing of the materials of the workpiece can be improved.

[0020] The increased plasticity volume extends across the entire width of the workpiece, and may extend, for example, through both the first and second components.

[0021] The first and second welding heads may be structurally identical, which can facilitate the provision of welds with consistent quality and strength across the entire width of the workpiece.

[0022] The first welding head and the second welding head may be structurally different. For example, the diameter of the first probe member may be larger or smaller than the diameter of the second probe member. The inner diameter of the first tubular shoulder may be larger or smaller than the inner diameter of the second tubular shoulder. The outer diameter of the first tubular shoulder may be larger or smaller than the outer diameter of the second tubular shoulder. In this way, an asymmetrical weld can be formed on the workpiece.

[0023] The first welding head may be equipped with a first clamp, and the second welding head may be equipped with a second clamp. The method may include a step of clamping the workpiece between the first clamp and the second clamp before rotating the first and second welding heads. This allows the workpiece to be fixed before welding, thereby ensuring welding accuracy and alignment of both sides of the workpiece. Furthermore, the clamp surrounding the tubular shoulder prevents lateral outward compression of the plasticizing material, thereby ensuring that the entire material is pushed into the workpiece as the probe and / or shoulder advance into the workpiece, and pressed into the recess created by the forward movement.

[0024] The method may include the steps of simultaneously rotating a first shoulder and a first probe member in the same direction, and simultaneously rotating a second shoulder and a second probe member in the same direction. Alternatively, the method may include the steps of simultaneously rotating a first shoulder and a first probe member in opposite directions, and simultaneously rotating a second shoulder and a second probe member in opposite directions. In this way, the introduction and mixing of heat in the area affected by the welding head may be further adjusted to the specific requirements of the components involved. In addition to selecting the direction of rotation of the probe member and tubular shoulder, their respective rotation speeds may also be adjusted according to the material and dimensional requirements of the workpiece.

[0025] Furthermore, the method may include a step of rotating the first probe member and the second probe member in the same direction. Alternatively, the method may include a step of rotating the first probe and the second probe in opposite directions. This provides further options for optimizing mixing and heat introduction in the welding area.

[0026] The second aspect relates to an apparatus for providing refill friction stir spot welding. The apparatus comprises a first welding head having a first probe member and a first tubular shoulder, wherein the first probe member is disposed inside the first tubular shoulder, axially aligned with the first tubular shoulder along a first head axis, and the first probe member is rotatable relative to the first tubular shoulder; a second welding head having a second probe member and a second tubular member, wherein the second probe member is disposed inside the second tubular shoulder, axially aligned with the second tubular shoulder along a second head axis, and the second probe member is rotatable relative to the second tubular shoulder. The apparatus further comprises a recess for positioning a welding object therein, the recess being disposed between the first welding head and the second welding head. The first welding head is disposed opposite to the second welding head, and the first welding head and the second welding head are axially movable along their respective first and second head axes so as to selectively engage a welding object positioned within the recess.

[0027] The apparatus may be configured such that the first welding head comprises a first clamp and the second welding head comprises a second clamp for clamping a welding object between the first clamp and the second clamp, thereby enabling the welding object to be fixed at a clearly defined position relative to the welding heads.

Brief Description of the Drawings

[0028] [Figure 1] A diagram showing an example of refill friction stir spot welding by a known method. [Figure 2] A diagram showing an example of refill friction stir spot welding according to the present disclosure. [Figure 3] A further example of refill friction stir spot welding, showing alternative forward and backward movement of the probe member and the tubular shoulder relative to the welding object. [Figure 4]This is a further example of refill friction stir spot welding, showing the alternative forward and backward movement of the probe member and tubular shoulder relative to the workpiece. [Figure 5] This is a diagram illustrating the described method, which includes an alternative welding object. [Figure 6] This is a diagram illustrating the described method with further alternative welded objects. [Modes for carrying out the invention]

[0029] Figure 1 shows an example of a refill friction stir spot welding process using a known method. Here, the welding head 10 comprises a probe member 2 and a tubular shoulder 4. A clamp 6 may also be optionally considered part of the welding head 10. The probe member 2 is cylindrical, while the tubular shoulder 4 is in the form of a cylindrical sleeve with a central recess. As shown in Figure 1, the probe member 2 is positioned in the central recess of the tubular shoulder 4, and both the probe member 2 and the tubular shoulder 4 are positioned around the central axis 8 of the welding head 10. Although not shown, both the probe member 2 and the tubular shoulder 4 are connected to a drive member configured to rotate both of them around the central axis 8 and to move both of them in a translational direction along the central axis.

[0030] During operation, the welding head 10 may be positioned near the workpiece 12, as shown in the leftmost figure of Figure 1. The workpiece 12 may be mounted on a support 14, as shown in Figure 1. The welding head 10 may then be moved axially to contact the workpiece 12, and may be pressed against the workpiece 12 with a predetermined force to apply pressure from the welding head 10 to the workpiece 12, as shown in the second figure from the left of Figure 1.

[0031] While maintaining pressure on the workpiece 12, both the probe member 2 and the tubular shoulder 4 may be rotated, thereby creating friction between the welding head 10, i.e., the probe member 2 and / or shoulder 4, and the workpiece 12, generating heat between them. The generated heat penetrates the material as the tubular shoulder 4 advances into the workpiece 12 from its initial position of contact with the workpiece 12, and the probe member 2 is withdrawn from its initial position of contact with the workpiece 12. The heat generated from the rotation of the probe member 2 and tubular shoulder 4 in contact with the workpiece 12 raises the temperature of the workpiece 12 near the welding head 10, creating a plasticized volume 16 in the workpiece, which becomes more malleable than the surrounding workpiece.

[0032] When the tubular shoulder 4 is driven into the plasticized volume 16 of the workpiece 12 and the probe member 2 is withdrawn from its initial position, the plasticized volume 16 moves upward toward the probe member 2 as it is displaced by the tubular shoulder 4 being driven into the workpiece 12.

[0033] After a predetermined time and displacement of the probe member 2 and tubular shoulder 4, both the probe member 2 and tubular shoulder 4 are returned to their initial positions, forcing the displaced plasticized material of the plasticized volume 16 back toward the workpiece 12, as shown in the second figure from the right in Figure 1. Finally, the rotation of the probe member 2 and tubular shoulder 4 may be stopped, and the welding head 10 may be removed from the surface of the workpiece 12 to cool the plasticized volume and harden the weld.

[0034] Figure 2 shows steps in a method and apparatus for providing refill friction stir spot welding according to the present invention. Here, a first welding head 110 and a second welding head 210 are shown. Each of the first and second welding heads 110, 210 comprises a first probe member 102 and a second probe member 202, and first and second tubular shoulders 104, 204. In this example, the first and second probe members 102, 202 are each cylindrical in shape and are positioned inside recesses formed in the respective first and second tubular shoulders 104, 204. Note that although the tubular shoulders 104, 204 have the shape of cylindrical sleeves, the central recess of the tubular shoulder needs to extend along its entire length. The first probe member 102 and the first tubular shoulder 104 are positioned so that their longitudinal axes align with the first head axis 108 of the first welding head 110. The second probe member 202 and the second tubular shoulder 204 are positioned so that their longitudinal axes align with the second head axis 208 of the second welding head 210. The first welding head 110 is equipped with a first clamp 106, while the second welding head 210 is equipped with a second clamp 206. In this example, the first and second clamps 106, 206 form part of the respective welding heads 110, 210 and are located radially outward of the respective first and second tubular shoulders 104, 204. The first and second clamps 106,206 may be in the form of cylindrical clamp members having recesses into which the respective first and second probe members 102,202 and tubular shoulders 104,204 are positioned.

[0035] The clamps 106,206 function to hold the respective probe members 102,202 and tubular shoulders 104,204 in place while forming a weld on the workpiece 112. Furthermore, the clamps 106,206 prevent the plasticizing material from escaping from the area beneath the shoulders 104,204.

[0036] Although not shown, the first probe member 102 and the first tubular shoulder 104 may be connected to a rotating device to enable their rotation. The first probe member 102 and the first tubular shoulder 104 may be rotatable relative to each other and therefore may be connected to a rotating device that enables their independent rotation, or each may be connected to a separate rotating device. Similarly, the second probe member 202 and the second tubular shoulder 204 may be coupled to a rotating device to enable their rotation, or may be rotatable relative to each other and may be coupled to a separate rotating device that enables their independent rotation, or to a single rotating device that enables such independent rotation.

[0037] As shown in the figure, in the example of Figure 2, the first welding head 110 and the second welding head 210 are positioned on both sides of the workpiece 112 such that the first head axis 108 of the first welding head 110 is aligned with the second head axis 208 of the second welding head 210. In this example, since the first welding head 110 and the second welding head 210 are geometrically identical, aligning the first welding head 110 with the second welding head 210 ensures balanced force application on both sides of the workpiece 112, and therefore, a balanced weld.

[0038] The first and second welding heads are also translatably movable toward or toward each other, for example, in the direction of their respective head axes 108,208 or parallel to the head axes 108,208.

[0039] Here, the object to be welded 112 consists of a first component 112a and a second component 112b. In this example, both the first and second components 112a and 112b are made from the same material, but it should be noted that this is not necessarily required, and the first and second components 112a and 112b may be made from different materials. The object to be welded 112 may have an overall thickness of 6 to 8 mm, which means that each component 112a and 112b may have a thickness of 3 to 4 mm. The object to be welded 112 is positioned in a recess 118 between the first welding head 110 and the second welding head 210. The object to be welded 112 may be held in place by any suitable means, such as an external arm, clamp, etc., which are not shown in Figure 2 for clarity.

[0040] As shown in the leftmost diagram of Figure 2, when the workpiece 112 is placed in the recess 118 between the first welding head 110 and the second welding head 210, the first and second welding heads advance toward each other in a direction aligned with their respective head axes 108, 208 until both the first and second welding heads 110, 210 make contact with the workpiece 112. In particular, the tip surfaces of the probe members 102, 202, the tubular shoulders 104, 204, and in this example, the clamps 106, 206 are also aligned with the surface of the workpiece 112 to take an "initial position" in contact with the workpiece 112. Pressure is then applied to the workpiece 112 through the first and second welding heads 110, 210, as indicated by the arrows 120, 220 in the second diagram from the left of Figure 2.

[0041] Now, moving to the central diagram in Figure 2, the probe members 102, 202 and the tubular shoulders 104, 204 are rotated simultaneously around their respective head axes 108, 208, as indicated by the arrows 122, 222.

[0042] The first shoulder 104 and the first probe member 102 may rotate in the same direction, and similarly, the second shoulder 204 and the second probe member 202 may rotate in the same direction. Alternatively, the first shoulder 104 and the first probe member 102 may rotate in opposite directions, and the second shoulder 204 and the second probe member 202 may rotate in opposite directions. In this way, the introduction and mixing of heat in the area affected by the welding heads 110, 210 may be further adjusted to the specific requirements of the workpiece 112. Furthermore, in any of the above options, the first probe member 102 and the second probe member 202 may rotate in the same direction or in opposite directions. In addition to selecting the direction of rotation for the probe members 102, 202 and the tubular shoulders 104, 204, their respective rotation speeds may also be adjusted according to the material and dimensional requirements of the workpiece 112.

[0043] As both the probe members 102,202 and the tubular shoulders 104,204 rotate while in contact with the workpiece 112, friction occurs between the tip surfaces of the rotating probe members 102,202 and the tubular shoulders 104,204, generating heat between them. This heat propagates through the workpiece, heating it and creating a volume 124 with increased plasticity within it. This volume with increased plasticity may be more malleable than the surrounding workpiece. The amount of heat generated may be varied by changing the rotation speed, direction of rotation, and the force with which the welding heads 110,210 (in this case, the tubular shoulders 104,204) are pressed into the workpiece 112. This can vary, for example, depending on the energy input required to plasticize a particular material of the workpiece 112, and / or the melting point of the material of the workpiece 112.

[0044] As the first and second probe members 102,202 and the first and second tubular shoulders 104,204 rotate, the tubular shoulders 104,204 advance (e.g., are driven) into the workpiece 112 and into the increased plasticity volume 124, as shown in the center diagram of Figure 2, while the probe members 102,202 are pulled out from their initial positions away from the workpiece 112. As shown in the center diagram of Figure 2, this has the effect of forming a recess 126 (in this case, a cylindrical recess) that is aligned with the head axis 108,208 and partially defined by the central recesses of each of the tubular shoulders 104,204. To avoid damage to either of the tubular members 104,204, contact between the tubular members 104,204 during operation may be avoided.

[0045] Although the probe members 102, 202 and the tubular shoulders 104, 204 are shown rotating in the same direction, it should be noted that they may rotate in different directions as already described above, which may provide a change in heat generation and thus provide the user with another variable for controlling the welding method.

[0046] As illustrated, the increased plasticity volume 124 extends throughout the entire thickness of the workpiece 112. This is due to the heat generated on both sides of the workpiece 112, and also because each welding head 110,210 benefits from the heat generated from the other welding head 210,110, thus creating a synergistic effect between the welding heads 110,210. In addition, this means that it may not be necessary to provide the same level of pressure and / or the same rotational speed, which means that the lifespan of the welding heads is extended.

[0047] Once the tubular shoulders 104,204 have advanced a predetermined distance into the workpiece (and the probe members 102,202 have been withdrawn a predetermined distance), the probe members 102,202 and the tubular shoulders 104,204 may return to their original positions (e.g., initial positions) after a predetermined time length. The time length may vary, for example, depending on the stiffness of the material of the workpiece 112 and its melting point. The predetermined distance may be equal between the tubular shoulders 104,204 and the probe members 102,202, or it may be based on the thickness of the first and second components 112a, 112b, which may be equal or unequal. For example, the predetermined distance between each tubular shoulder 104,204 may be 50%, 45%, 40%, etc., of the thickness of the workpiece 112, or it may be the total thickness of each first or second component 112a, 112b, or 95%, 90%, etc., of the thickness of each component 112a, 112b.

[0048] When the probe members 102, 202 and the tubular shoulders 104, 204 are returned to their original positions, the increased plasticity volume 124 is pushed back to the original volume of the workpiece 112. The rotation of the probe member 112 continues while the probe members 102, 202 are returning, and the tubular shoulders 104, 204 are maintained until the probe members 102, 202 and the tubular shoulders 202, 204 return to their initial positions. The described movement of the probe members 102, 202 and the tubular shoulders 202, 204 may have the effect of mixing the plasticity volumes that span both components 112a and 112b of the workpiece.

[0049] Next, the welding heads 110 and 210 may be withdrawn from the workpiece 112, and the plasticized volume may be cooled, thereby solidifying the plasticized volume together to form the weld volume.

[0050] The first and second probe members 102,202, and the first and second tubular shoulders 104,204 are shown to be the same size, but this is not necessarily required. For example, one of the first and second probe members 102,202 may have a larger or smaller diameter than the other, and therefore the corresponding inner diameters of the tubular shoulders 104,204 may also be different. Furthermore, the outer diameter of one tubular shoulder 104,204 may be larger or smaller than the other. Therefore, the shape and strength of the plasticized volume may vary accordingly.

[0051] Figure 3 shows another example of a method for providing refill friction stir spot welding. Many of the features in Figure 3 are the same as those described in Figure 2 and are therefore not repeated.

[0052] As described above, the first and second welding heads 110 and 210 are shown, each comprising first and second probe members 102 and 202, first and second tubular shoulders 104 and 204, and first and second clamps 106 and 206. As is clear from Figure 3, only the central figure differs from the figure in Figure 2.

[0053] According to the method shown in Figure 3, the first probe member 102 is rotated and advanced into the workpiece 112, while the second probe member 202 is also advanced into the workpiece 112 from its initial position. In parallel, the first and second tubular shoulders 104, 204 are withdrawn from the workpiece 112, in contrast to the diagram in Figure 2. In this example, the first and second probe members 102, 202 are advanced into the welding material.

[0054] As shown in the figure, one recess defined by probe members 102, 202 is formed containing a volume of plasticizing material. This volume 126 is defined by the first and second probe members 102, 202. To form this volume, the first tubular shoulder 102 and the second probe member 202 may be advanced into the workpiece 112 by less than 50% of the width or thickness of the workpiece. Here, a single volume can improve the mixing of the material in the plasticizing volume and may result in a preferred weld strength for some applications compared to the figure in Figure 2.

[0055] Figure 4 shows a further example of a method for providing refill friction stir spot welding. Many of the features in Figure 4 are common to those described in Figures 2 and 3 and are therefore not repeated.

[0056] As described above, the first and second welding heads 110 and 210 are shown, each comprising first and second probe members 102 and 202, first and second tubular shoulders 104 and 204, and first and second clamps 106 and 206. As is clear from Figure 4, only the central figure differs from the figures in Figures 2 and 3.

[0057] According to the method shown in Figure 4, the first tubular shoulder 104 rotates and advances into the workpiece 112 as shown in Figure 2, while the second probe member 202 advances into the workpiece 112 from its initial position, while the second tubular shoulder 204 is withdrawn from the workpiece 112, in contrast to the diagram in Figure 2. In this example, the second probe member 202 is advanced into the welding material so that it is partially positioned within the recess of the first tubular member 104. However, it should be noted that in some other examples, the second probe member 202 and the first tubular shoulder 104 may be advanced a smaller distance into the workpiece 112 so that the second probe member 202 is not positioned within the first tubular shoulder 104.

[0058] As shown in the figure, instead of forming a single recess defined by the tubular shoulders 104, 204 (e.g., the inner surfaces of the tubular shoulders) and the probe members 102, 202 (e.g., the tip surfaces of the probe members 102, 202), two recesses containing volumes of plasticizing material are formed here. Of these volumes, the first volume 126a is defined by the inner surface of the first tubular shoulder 104 and the tip surfaces of the first and second probe members 102, 202, while the second volume 126b is defined by the outer surface of the second probe member 202, the tip surfaces of the tubular shoulders 104, 204 and the second clamp 206. To form these volumes, the first tubular shoulder 104 and the second probe member 202 may be advanced into the workpiece 112 beyond 50% of the width of the workpiece. The presence of two separate volumes allows for improved mixing of the plasticized volume material, which, compared to the diagram in Figure 2, can result in favorable weld strength for several applications.

[0059] In this example, the distance the first shoulder 104 advances into the workpiece 112 is only slightly greater than the thickness of the first component 112a, and therefore only the surface area of ​​the second component 112b adjacent to the first component 112a is essentially affected; that is, the first shoulder 104 simply "grabs" the second component 112b. Similarly, the distance the second probe member 202 advances into the workpiece 112 is only slightly greater than the thickness of the second component 112b, and therefore only the surface area of ​​the first component 112a is essentially affected by the second probe member 202; that is, the second probe 202 simply grazes the first component 112a.

[0060] Furthermore, Figure 5 shows a fourth example of a method for providing refill friction stir spot welding. In this example, the same movement of the welding heads 110, 210 as in Figure 2 is performed, but the workpiece to be welded consists of first, second, and third components 112a, 112b, and 112c, with the third component 112c positioned between the first and second components 112a, 112b. Here, the first and second components 112a, 112b are made of the same material, e.g., aluminum, while the third component 112c is made of a different material, e.g., titanium. In this example, two plasticizing volumes 124a, 124b are present in the first and second components 112a, 112b of the workpiece 112. The melting point of the third component 112c may be higher than that of the first and second components 112a and 112b. Therefore, no plasticized volume may be formed in the third component 112c, or a plasticized volume with reduced plasticity may be formed compared to the plasticized volumes of the first and second components 112a and 112b. It should be noted that the first and second components 112a and 112b may be made of different materials, such as magnesium and copper.

[0061] According to this method, the tubular shoulders 104, 204 may advance into the workpiece 112 by a distance less than or equal to the thickness of the respective first component 112a or second component 112b, and the plasticized volumes 124a, 124b may form two welds on the surface of the third component 112c. However, the distance that the first and second shoulders 104, 204 advance into the first and second components 112a, 112b is slightly greater than the thickness of each component, and therefore, the surface area of ​​the third component 112c may also be affected by the first and second shoulders 104, 204.

[0062] Furthermore, Figure 6 shows a fifth example of a method for providing refill friction stir spot welding. In this example, the same movement of the welding heads 110, 210 is performed as in Figure 2. However, the workpiece 112 is composed of multiple components formed as a multilayer arrangement. Here, the components may be made of the same material, or they may be made of alternating materials, such as aluminum and copper, as used in battery technology. In this example, it can be seen that a single continuous plasticizing volume 126 exists within the multiple components, and that stir spot welding can be formed within a multilayer structure using the method of the present invention.

[0063] Although the above methods were described separately, it should be noted that these are merely illustrative examples of possible methods, and steps described in relation to one method may be applicable to another. For example, the movement of the probe members 102, 202 and tubular shoulders 104, 204 described in Figures 3 and 4 may be applicable to methods having three or more component weld objects 112 as shown in Figures 5 and 6.

Claims

1. A method for performing refill friction stir spot welding, A step of providing a first welding head (110) comprising a first probe member (102) and a first tubular shoulder (104), wherein the first probe member (102) is positioned inside the first tubular shoulder (104) and is axially aligned with the first tubular shoulder (104) along a first head axis (108), A step of providing a second welding head (210) comprising a second probe member (202) and a second tubular shoulder (204), wherein the second probe member (202) is positioned inside the second tubular shoulder (204) and is axially aligned with the second tubular shoulder (204) along a second head axis (208), The steps include positioning the first welding head (110) on the first surface such that the first probe member (102) and the first tubular shoulder (104) are in contact with the first surface of the workpiece to be welded, The steps include positioning the second welding head (210) on the second surface facing the first surface such that the second probe member (202) and the second tubular shoulder (204) are in contact with the second surface of the object to be welded (112), and the first head shaft (108) is aligned with the second head shaft (208), The steps include simultaneously rotating the first and second welding heads so as to form an increased plastic volume in the workpiece near the first and second welding heads, Steps include: advancing one of the first probe member (102) and the first tubular shoulder (104) and one of the second probe member (202) and the second tubular shoulder (204) from their initial positions along their respective first and second head axes (108, 208) to their respective first and second surfaces of the workpiece (112); and retracting the other of the first probe member (102) and the first tubular shoulder (104) and the other of the second probe member (202) and the second tubular shoulder (204) from their initial positions along their respective first and second head axes (108, 208); The steps include returning each of the first and second probe members (102, 202) and the first and second tubular shoulders (104, 204) toward the initial position, The steps include removing the first and second welding heads (110, 210) from the first and second surfaces of the workpiece (112), A method for performing refill friction stir spot welding, including the method described above.

2. A method for performing refill friction stir spot welding according to claim 1, comprising the step of simultaneously advancing the first tubular shoulder (104) and the second tubular shoulder (204) from their initial positions along their respective first and second head axes (108, 208) into their respective first and second surfaces of the workpiece (112) to be welded, while retracting the first and second probe members (102, 202) from their initial positions along their respective first and second head axes (108, 208).

3. The object to be welded (112) comprises first and second components (112a, 112b) positioned between the first and second welding heads (110, 210), wherein the first component (112a) has the first surface, and the second component (112b) has the second surface. A method for performing refill friction stir spot welding according to claim 2, wherein the method includes the steps of advancing the first tubular shoulder (104) into the workpiece to be welded (112) by a distance less than or equal to the thickness of the first component (112a), and advancing the second tubular shoulder (204) into the workpiece to be welded (112) by a distance less than or equal to the thickness of the second component (112b).

4. A method for performing refill friction stir spot welding according to claim 1, comprising the step of simultaneously advancing the first tubular shoulder (104) and the second probe member (202) from their respective initial positions along their respective first and second head axes (108, 208) into their respective first and second surfaces of the workpiece (112) to be welded, while retracting the first probe member (102) and the second tubular shoulder (204) from their respective initial positions along their respective first and second head axes (108, 208).

5. The object to be welded (112) comprises first and second components (112a, 112b) positioned between the first and second welding heads (110, 210), wherein the first component (112a) has the first surface, and the second component has the second surface, and the first and second components (112a, 112b) comprise these first and second components (112a, 112b). A method for performing refill friction stir spot welding according to claim 4, wherein the method includes the steps of advancing the first tubular shoulder (104) into the workpiece to be welded by a distance greater than the thickness of the first component (112a), and advancing the second probe member (202) into the workpiece to be welded by a distance greater than the thickness of the second component (112b).

6. A method for performing a refill friction stir spot welding according to claim 4 or 5, comprising the step of advancing the first tubular shoulder (104) and the second probe member (202) into the workpiece (112) such that the second probe member (202) is partially positioned within the first tubular shoulder (104).

7. The workpiece to be welded (112) comprises first and second components (112a, 112b) positioned between the first and second welding heads (110, 210), wherein the first component (112a) has a first surface and the second component (112b) has a second surface, and a third component (112c) positioned between the first and second components (112a, 112b), The method comprises the steps of advancing one of the first probe member (102) and the first tubular shoulder (104) along the first head axis (108) into the workpiece (112) by a distance greater than, equal to, or less than the thickness of the first component (112a), and advancing one of the second probe member (202) and the second tubular shoulder (204) by a distance greater than, equal to, or less than the thickness of the second component (112b). A method for performing refill friction stir spot welding according to claim 1, comprising the step of advancing the first probe member (102) and the other of the first tubular shoulder (104), and the second probe member (202) and the other of the second tubular shoulder (204), from their initial positions along the first and second head axes (108, 208), respectively.

8. A method for performing refill friction stir spot welding according to claim 1, comprising the steps of advancing the first probe member (102) and the second probe member (202) from their initial positions along their respective first and second head axes (108, 208) into their respective first and second surfaces of the workpiece (112) to be welded, while retracting the first tubular shoulder (104) and the second tubular shoulder (204) from their initial positions along their respective first and second head axes (108, 208).

9. A method for performing refill friction stir spot welding according to claim 1, wherein the first welding head (110) comprises a first clamp (106) and the second welding head (210) comprises a second clamp (206), and the method includes the step of clamping the workpiece (112) between the first clamp (106) and the second clamp (206) before rotating the first and second welding heads (110, 210).

10. The process includes the step of simultaneously rotating the first tubular shoulder (104) and the first probe member (102) in the same direction. A method for performing refill friction stir spot welding according to claim 1, comprising the step of simultaneously rotating the second tubular shoulder (204) and the second probe member (202) in the same direction.

11. The process includes the step of simultaneously rotating the first tubular shoulder (104) and the first probe member (102) in opposite directions. A method for performing refill friction stir spot welding according to claim 1, comprising the step of simultaneously rotating the second tubular shoulder (204) and the second probe member (202) in opposite directions.

12. A method for performing refill friction stir spot welding according to claim 10 or 11, comprising the step of rotating the first probe member (102) and the second probe member (202) in the same direction.

13. A method for performing refill friction stir spot welding according to claim 10 or 11, comprising the step of rotating the first probe member (102) and the second probe member (202) in opposite directions.

14. Apparatus for providing refill friction stir spot welding, A first welding head (110) comprising a first probe member (102) and a first tubular shoulder (104), wherein the first probe member (102) is positioned inside the first tubular shoulder (104), is axially aligned with the first tubular shoulder (104) along a first head axis (108), and the first probe member (102) is rotatable relative to the first tubular shoulder (104), A second welding head (210) comprising a second probe member (202) and a second tubular shoulder (204), wherein the second probe member (202) is positioned inside the second tubular shoulder (204), is axially aligned with the second tubular shoulder (204) along a second head axis (208), and the second probe member (202) is rotatable relative to the second tubular shoulder (204), A recess for positioning the object to be welded (112) therein, wherein the recess is positioned between the first welding head (110) and the second welding head (210), Equipped with, The first welding head (110) is positioned opposite the second welding head (210), and the first welding head (110) and the second welding head (210) are axially movable along their respective first and second head axes (108, 208) so as to selectively engage with the workpiece (112) positioned within the recess. The aforementioned device is The first and second welding heads are rotated simultaneously so as to form an increased plastic volume in the workpiece near the first and second welding heads. One of the first probe member (102) and the first tubular shoulder (104), and one of the second probe member (202) and the second tubular shoulder (204), are simultaneously advanced from their initial positions along their respective first and second head axes (108, 208) to the respective first and second surfaces of the workpiece (112), while the other of the first probe member (102) and the first tubular shoulder (104), and the other of the second probe member (202) and the second tubular shoulder (204), are retracted from their initial positions along their respective first and second head axes (108, 208). The first and second probe members (102, 202) and the first and second tubular shoulders (104, 204) are each returned to their initial positions. The first and second welding heads (110, 210) are removed from the first and second surfaces of the workpiece (112), respectively. An apparatus for providing refill friction stir spot welding, configured as such.

15. An apparatus for providing refill friction stir spot welding according to claim 14, wherein the first welding head (110) comprises a first clamp (106), and the second welding head (210) comprises a second clamp (206) which clamps the workpiece (112) to be welded between the first clamp (106) and the second clamp (206).

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